The present invention relates to a cruise control apparatus for a vehicle which is capable of making the vehicle travel at a predetermined constant speed in an automatic manner.
There has been known a conventional cruise control apparatus for a vehicle in which the target speed at which the vehicle is to travel is determined as the speed of the vehicle sensed by a speed sensor at the instant when the operator turns on a cruise control switch. The target speed thus determined is then stored in a RAM in a microcomputer. Based on the present speed as continuosly sensed by the speed sensor every second and the target speed, an amount of opening of a throttle valve in the intake manifold of the engine which corresponds to the target speed is calculated by the microcomputer. Then, the throttle valve is set to the thus calculated opening amount through the action of an actuator so that the speed of the vehicle is adjusted to the target speed.
However, with the conventional cruise control apparatus constructed in the above manner, if the microcomputer writes, due to external noise or the like, into the RAM incorrect data different from the correct data for the target speed, the cruise control apparatus operates to maintain a speed level different from the target speed.